Gregoryite was named after Professor John Walter Gregory (associated with the University of Melbourne, Australia and the University of Glasgow, Scotland), and was discovered in 1980.
Properties of Gregoryite
The following are the key properties of gregoryite:
- Cell Data
- Space group: P63mc (synthetic)
- a = 5.215
- c = 6.584
- Z = 2
- Crystal Data
- Point group: 6mm
- As minute imperfect rounded crystals
- X-ray powder pattern: Synthetic (ICDD 25–815)
- 2.66 (100), 2.61 (75), 3.29 (40), 2.137 (40), 1.863 (30), 3.72 (27), 1.707 (8)
- Chemical Composition
|-O = (F, Cl)2
- Optical Properties
- Optical class: [Uniaxial]
- ω = n.d.
- ε = n.d.
- Estimated Properties
||Bulk density (electron density)=2.42 gm/cm3
note: Specific gravity of gregoryite =2.46 gm/cm3
||PEGregoryite = 2.98 barns/electron
U=PEGregoryite x ρelectron= 7.21 barns/cm3
||Fermion index = 0.001419959
Boson index = 0.998580041
|GRapi = 289.43 (Gamma Ray American Petroleum Institute Units)
Concentration of gregoryite per GRapi unit = 0.35 (%) Estimated radioactivity from gregoryite - barely detectable
How to Identify Gregoryite
Gregoryite is a rare mineral that can be identified in the field by its white color and white streak. The density of this mineral is 2.27 gm/cm3.
The only known locality of gregoryite is in Tanzania’s Oldoinyo Lengai volcano.
Occurrence of Gregoryite and Useful Mineral Associations
Gregoryite occurs as phenocrysts in lengaite carbonatite lava. It's often associated with minerals such as halite, nyerereite, alabandite, fluorite, calcite, and sylvite.